2eighTZ4me Posted August 18, 2008 Share Posted August 18, 2008 A little background. I bought a n47 head with a Racer Brown cam kit in it. The lash pads are .240". The top retainers are deep. With the .240" lash pads (that came with the head/kit) the wipe pattern is very close to the valve side. Rockers go from 1 - 12 starting at the right and moving left. For grins, I tried a stock .120" lash pad. The wipe pattern is "better". but a little too much toward the pivot side. The .120" pad was used on the far right rocker in the pic. A potential problem I foresee, is the depth at which the stock lash pad sits down in the upper spring perch. The .120" is on the left, the .240" is on the right. Am I going to have problems here? I did Braap's trick of cutting up some feeler gauges and laying them on top of the lash pads and came up with a nice wipe at about .205" So, MSA sells them in .010" increments. Should I go with .200" or .210"? I've read other threads here on this subject, and the consensus seems to be to lean toward the pivot point, which would mean .200" Am I correct here? I also, however, read in the "How to Modify" book, that they want the contact patch dead center, which would mean going to a .210" here, as there is just a weee bit more wipe on the pivot side as opposed to the valve side. What say ye O' great builders of the coveted L series? BTW - these are resurfaced stock rockers that Delta Cams did. I measured about a .035" difference in thickness of the pad between one of the "new" units I got from MSA and the re-surfaced one from Delta. Is this going to throw off cam geometry when it's all said and done? I performed all wipe patterns at .008" clearance intake and .010" clearance exhaust. I now know why my first Schneider cam got munched. MSA is supposed to sell the cam kits with .170" lash pads - I got stock lash pads (actually .115") with my kit. Now I know better to do the wipe pattern - hey - everybody screws up a few times! Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted August 19, 2008 Share Posted August 19, 2008 I would lean towards the pivot from what I have read here at HBZ. I even heard that it's not a huge deal if the wipe pattern runs right to the edge of the pad on the pivot side. It actually increases your rocker ratio, leading to more lift if that's what you want. Mine are slightly off center towards the pivot arm. I was able to carefully file down a factory shim by hand to get the wipe pattern where I wanted. Not sure if it's going to hold up because the head is still on my bench. I suspect it will be fine. Quote Link to comment Share on other sites More sharing options...
Daeron Posted August 19, 2008 Share Posted August 19, 2008 Good question, good pictures.. posting to subscribe in hopes of detailed answers from others. Thanks! Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted August 19, 2008 Author Share Posted August 19, 2008 So - unless instructed otherwise, it looks like the .200's are in my near future. Hoping others will chime in. It doesn't seem like rocket science, but it is a very crucial step for setting up valvetrain. Thanks all! Quote Link to comment Share on other sites More sharing options...
Phred Posted August 20, 2008 Share Posted August 20, 2008 If you have a dial indicator, check the lift of each valve. I have set up many heads with different sized lash pads on the same head to equalize the lifts. The wipe may look the same, but the lifts my vary. Setting up for equal lifts is most important when valve to piston clearences are getting close. Also, if you have equal lifts the fuel curve will be equal on all cylinders, leading to even EGT's. All this is usually done on a racing engine, but if you have the time, it makes for a nice running street engine too. Phred Quote Link to comment Share on other sites More sharing options...
1 fast z Posted August 20, 2008 Share Posted August 20, 2008 If you have a dial indicator, check the lift of each valve. I have set up many heads with different sized lash pads on the same head to equalize the lifts. The wipe may look the same, but the lifts my vary. Setting up for equal lifts is most important when valve to piston clearences are getting close. Also, if you have equal lifts the fuel curve will be equal on all cylinders, leading to even EGT's. All this is usually done on a racing engine, but if you have the time, it makes for a nice running street engine too.Phred How do you know if the valves are all the same depth, in relation to the pistons? Just because you set equal lift, you also need to check the initial distance from piston to valve on each cylinder. Have you verrified CC's on each intake runner, as well as port volume? This needs to come into play also, if trying to equalize out a Valve system. So to acheive what you are describing, all of these factors need to come into play. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 20, 2008 Share Posted August 20, 2008 How do you know if the valves are all the same depth, in relation to the pistons? Shouldn't a proper valve job include verifying that the valves are all at the same depth when closed? I know my machinist made sure of that. Once you have the valve height squared away, then the lift would be the same as measured on the valve tip with the dial indicator. It's a good idea, and something that never even remotely crossed my mind. Thanks for the tip Phred! Quote Link to comment Share on other sites More sharing options...
1 fast z Posted August 20, 2008 Share Posted August 20, 2008 Was his head indeed done the correct way by setting each valve within a couple thousands to the deck of the head??? Most and I mean 90% of shops wont do it the correct way. Quote Link to comment Share on other sites More sharing options...
Tony D Posted August 20, 2008 Share Posted August 20, 2008 Personally, I'd run the .120" pads, as the ratio is better that way, you get more lift. I'd get spring retainers that allowed that. It looks like you would have to go with cut down spring retainers anyway the way those .240's fit in there, so if you cut em down for .200's why not take another .080 or .100 off so you can use the .120's and get the most advantageous ratio possible? A centered wipe pattern is 'nice' but not necessarily 'the most performance oriented'... As long as you have 2mm of wipe pattern on the pivot side, I'd be happy with that. In any of these cases, you will likely have to do something about those spring retainers (Upper Spring Perch) to allow thinner pads to be installed. Less weight, more revs...muahahahaha! Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted August 20, 2008 Author Share Posted August 20, 2008 OK - I took a few more pics with the .120" lash pad to get your opinions. I can't really fit a feeler gauge in between the rocker and the retainer top, but I do believe there is enough clearance to make it work without having to go do different retainers. This is the setup (adjusted to .010 lash - exh.) under full compression. Note the lobe almost dead center on the rocker. I don't see any rubbing on the top of the retainer. Also, the pivot ball is adjusted way up due to the thin lash pad, giving a greater angle and better clearance. It is difficult to get good shots due to close proximity. The above and 2 pics below are under no compression of the spring. Based on Tony D's reply, I have a few questions. 1) If I need retainers with a shorter "top", is it possible to use stock retainers in place of these - using stock keepers as well? Keeping the Racer Brown springs only. 2) Could I grind down the tops of these retainers for more clearance? 3) Should the lash pad top surface ALWAYS be parallel with the top of the retainer - meaning, are they matched somehow? (See the pic of the .240" pad above in post #1 - it's dead even with the top of the retainer) I would think not, based on the fact that you tune your wipe pattern via the lash pad, and it would be costly (and a PITA) to have to swap out retainers every time you went with a different size lash pad. I got a set of .200"'s on the way, but I like the idea of better performance and more lift as Tony mentioned by using the .120"s. I have plenty of spare stock retainers and keepers, so I have options. Just want to see "what" my options are in this situation. I'd rather leave the current retainers in place and use the .120" lash pad, as I see some clearance, but things undoubtedly change at 7500 rpm..... I don't believe I've ever seen a set of retainers with this deep of a dish (.240"). The Schneider ones definitely weren't. Thanks for all your great replies - keep 'em coming! Quote Link to comment Share on other sites More sharing options...
Phred Posted August 21, 2008 Share Posted August 21, 2008 I agree completely. And yes I do these things, and have been for thirty years or so. Checking lift is just a simple thing that most people can do. As long as they are setting up the lash, why not? Also, any decent shop with a DCM, Rottler, Sunnen, etc. will be happy to do some equalizing of valve heights if you ask. If they can't, go somewhere else. Most people here are enthusiasts, and those of us in the business should offer support and options whenever we can. Phred Quote Link to comment Share on other sites More sharing options...
1 fast z Posted August 21, 2008 Share Posted August 21, 2008 I use a Matsuura CNC Mill to set my heights. Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted August 21, 2008 Author Share Posted August 21, 2008 OK - well, I was hoping for information on the topic and not what types of machines you guys use. I realize it is probably important to set the valve lifts, but my concern is the lash pads and wipe patterns - most particularly, if I can get away with running the .120" lash pads without fear of screwing something up. See pics above. Quote Link to comment Share on other sites More sharing options...
1 fast z Posted August 21, 2008 Share Posted August 21, 2008 Yes you can run the stock retainers, as long as the spring ID and OD of both of them fits the retainer, and no bind occures during lift. The only benifit to the aftermarket retainers is that they are deeper, which allow for the taller pad support. The keepers should be identical, unless you changed to a different degree, but I dought it. Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted August 21, 2008 Author Share Posted August 21, 2008 Sweet! Thanks Bryan - that's EXACTLY what I'm looking for. Quote Link to comment Share on other sites More sharing options...
1 fast z Posted August 21, 2008 Share Posted August 21, 2008 NO, prob, guess I should of answered the direct question in the begining, but then we would not have got a discussion out of it! Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted August 29, 2008 Author Share Posted August 29, 2008 OK, following Bryan's advice, I went with the stock retainers and kept the Racer Brown springs. I've noticed a considerable drop in installed spring height, as well as the coils being closer together. Stock retainer on left, Racer Brown retainer on right. Here's a better picture of the coil rate I'm not seeing any bind in the coils at full lift, I am able to stick a .015" feeler gauge between the middle coils - even though it looks spring bound. This is with the .200" lash pads installed. I actually have a wipe pattern that looks acceptable! I am, however, going to drop to either a .170 or .180 on #'s 6, 9, and 12 until I get it just right. So - thousand dollar question - am I going to run into problems using the stock retainers with the Racer Brown springs, being that the spring is compressed more at "rest"? The problem with the Racer Brown retainers is that the .240" lash pads fit in there fine, but give a bad wipe pattern, while the .200's that I bought from Nissan won't fit down in the bore of the top of the retainer. Do I need to go back to the Racer Brown retainers and have them machined just a wee bit more to accept the factory lash pads?? I've got so much money tied up in this head with port work, valve seats, valve job etc, that I'd hate to screw something up at high rpm. Suggestions / comments always welcomed! Let's hear it. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 29, 2008 Share Posted August 29, 2008 You should have a closed spring rate and an open spring rate that are "reasonable". I can't remember what "reasonable" is, it's been years since I dealt with this last, but running the springs more compressed like that will mean that the seat pressure is higher and basically you're looking at more wear on the cam and rockers as a result. I would suggest that you find out what is reasonable and where you are. You'll need to find a shop with a valve spring rate tester. Quote Link to comment Share on other sites More sharing options...
Phred Posted August 30, 2008 Share Posted August 30, 2008 In one of your pics, I can see 3 or 4 spring shims under the spring seat. Get rid of those, and your installed/open pressure will more reasonable. Generally, .060 over coil bind is acceptable, .015 is not. I have run springs closer than .060, but there is no need to for your set up. Jon has the right idea. You need to know what the installed, and open pressures are. If you don't know how to do this you will have to take the complete head to an engine shop. They will measure the installed height, then put the springs in a valve spring pressure tester. To find open pressure, you subtract the amount of net valve lift from the installed height. Then check the spring at that height. Anything over 220 lbs. open, for a street/race engine is too much. Most aftermarket race springs are too heavy for the street, and some discretion is need here. For example, 250 lb. (open) is enough to control valve float ( with steel valves ) at 8000 rpm on an L6. And 250 lbs. can control Ti valves at 9000 rpm. Most engine shops that are not familiar with L engines tend to over-spring. I have taken heads apart that have 350 lbs. open pressure, and they only turn 7500 rpm. All that does is waste HP, and wear every thing out in a big hurry. Some cam manufacture's have spring pressure charts that are included with the purchase of valve springs. If you have one, this can be a good start to finding the correct pressure for your particular engine. Phred Quote Link to comment Share on other sites More sharing options...
Careless Posted August 30, 2008 Share Posted August 30, 2008 I was just going to mention that .015 sounds pretty dangerous with something that is "springy", but Phred said it better. Quote Link to comment Share on other sites More sharing options...
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